Data cleanliness is never a solved problem, it's just a fact. Depending on how severe the problem is, a simple way to combat this is by adding a custom key/valu

Data cleanliness is never a solved problem, it's just a fact. Depending on how severe the problem is, a simple way to combat this is by adding a custom key/value pair to all client-side GA requests (custom dimensions are great for this) and then adding a filter to your profile within the Google Analytics admin to exclude all requests without the appropriate key value. Change the value on a recurring basis, how often is your preference. Though always be sure you have at least 2 profiles for any GA property, one filtered (Production) and one unfiltered as the C.Y.A. profile so that should anything go wrong, you can still get to all data.